This invention relates to a local area network, and, more particularly, to a bus-configured local area network with data exchange capability.
With recent office automation, various electronic devices such as facsimiles and computers are extensively used, and there is a demand for a local area network with data exchange capability for terminals including electronic devices and telephone sets. However, it is very difficult to directly connect all terminals to a private branch exchange (PBX), as in an existing network using a PBX.
The difficulty can be alleviated by providing each area, such as a building or a building floor, with a local equipment to which terminals are connected. A simplified local-area network architecture may be realized by connecting each local equipment to a point of the bus wired from PBX, serving as a central equipment, instead of directly connecting each local equipment thereto. In such a bus-configured local-area network, signal transmission and reception is achieved by a time-division multiplexing system.
The bus-configured local-area network suffers from such a disadvantage as described below. Since the signal transmission time between the central equipment and each local equipment varies with the point at which the local equipment is connected to the bus, and the signal transmission and reception is done in a time-division manner, collision and overspace are liable to occur between signals sent from different local equipments to the central equipment. It is evident that the collision of signals is undesirable for signal transmission and reception. The overspace reduces signal transmission efficiency.